Mr Trump claimed on Twitter that North Korea's plans to put America in range of a nuclear missile "won't happen." The tweet was sent in response to leader Kim Jong-un claiming North Korea is close to testing an intercontinental ballistic missile.

Klaas, a fellow at the London School of Economics and an expert on international affairs, told Julia Hartley-Brewer "the fact [North Korea] have nuclear capabilities means we’re right to be worried" and said it's "worrisome that Donald Trump is stirring the pot on Twitter. I think that’s really dangerous for someone to do, before they’re even in office.

“Trump is very willing to just poke things and see what happens and sometimes that’s going to backfire," he added. “Trump’s advisors, I hope, will stop him from talking about foreign policy crises on Twitter. It’s just not the right avenue for it."